This invention relates to medical devices, and in particular to angiographic catheters. Angiographic catheters are long, narrow, thin-walled tubes that are percutaneously inserted into the human or animal vascular system for therapeutic or diagnostic purposes. Most diagnostic catheters have a series of side-holes in varied configurations near the distal end, as well as an open end-hole at the distal end tip. The end-hole allows the catheter to be passed over and guided by a wire which has been inserted into the vascular system through a hollow cannula placed in a blood vessel, after which the guide wire is withdrawn. The smaller side-holes and end-hole allows injection of radiopaque contrast material into the blood stream surrounding the distal end, so as to produce an image of the outline of a chamber or a blood vessel (an angiogram) on X-ray film or other graphic medium. During the diagnostic angiography process, the contrast material is normally injected at a rapid rate using a power injector. The contrast material is forcefully discharged from the end-hole and side-holes at the distal end of the catheter.
Problems with forceful discharge of contrast material through the end-hole and smaller side-holes of an angiographic catheter are manifest. Forceful discharge can create a jet effect. The end-hole jet effect produces undesirable recoil of the catheter, thereby shifting the catheter from a desired position within a chamber or a vessel, e.g. aortic root. Catheter jets can also produce a dangerous complication, subintimal injection of the contrast material, in which the jets tunnel into the wall of the blood vessel, sometimes resulting in acute occlusion of the vessel and in a chamber like left ventricle can cause subintimal injection resulting in significant damage to endothelium. When dye is injected in a chamber like left ventricle, an end-hole or side-hole jet can also cause premature ventricular contractions (PVCs), ventricular tachycardias (groups of three or more PVCs) and other arrhythmias which endanger the patient, lengthen the time of exposure to X-rays required for satisfactory opacification, and often result in unintelligible chamber opacification in an angiogram made during their occurrence.
A further complication resulting from pressurized discharge of contrast material through the end and side-holes of known catheters is the need for more contrast material than is optimally desired to produce the angiogram. Available angiographic catheters require as much as 50 to 55 milliliters (ml) of contrast material to satisfactorily outline a human ventricle. Currently available contrast material can cause undesirable generalized allergic reactions like anaphylaxis and renal failure. Also, the amount of material used dictates the time required to inject the material and, therefore, affects both the required length of exposure to dangerous X-rays as well as the probability of obtaining a satisfactory angiogram. There is, therefore, a need in the field to reduce the amount of contrast material used in cardiac angiography.
Most catheters presently used for rapid flush angiography are configured with a circular loop or xe2x80x9cpigtailxe2x80x9d at the distal end. These pigtail-type catheters are provided with a plurality of side-holes through which only approximately 40% of the contrast medium is discharged at the desired position within the chamber. Although the looped end of the catheter decreases somewhat the chance of subintimal injection, the open end-hole still allows approximately 40% of the contrast material to exit the end-hole. The material exiting the end-hole creates a strong jet of material placed away from the optimal position for vessel or chamber opacification. To overcome the limitations of the pigtail catheter in cardiac angiography, various modifications have been attempted to the pigtail configuration, such as a bend at an acute angle in the distal portion of the catheter and adding multiple holes on the shaft, both to decrease the jet effect. However, these modifications have not satisfactorily alleviated the problems associated with the use of any catheter which has an open end-hole.
The smaller side-holes located adjacent the distal end of known angiographic catheters are flawed as well. Such side-holes allow a very limited volume of material to form the bolus needed for opacification of the chamber, thereby elongating the time needed to adequately outline the chamber in the angiogram. Longer X-ray exposure endangers the patient and decreases the likelihood of obtaining satisfactory angiogram results. Moreover, side-holes can cause pressure jets leading to PVCs and other arrhythmias, as outlined above.
Although adding additional side-holes may increase the volume of material allowed into the vessel while dissipating pressure jets, such an increase may result in a distal region of less strength than the main body of the catheter tube. As a result of this reduced strength, complaints have arisen as to some currently-available angiographic catheters from physicians, who have reported that in clinical use, as they have attempted to put the pigtail tip through the aortic valve, the distal tip area in which the side-holes reside sometimes buckles.
It is therefore desirable to increase the volume of the bolus of contrast material allowed to flow out of an angiographic catheter in a short time span without decreasing the catheter""s rigidity near the distal end, and without inducing PVCs, ventricular tachycardias or other arrhythmias. It is also desirable to decrease the amount of material needed to create the bolus of material within the opacified vessel.
This invention is directed to an endocardial catheter. The catheter preferably incorporates an end-hole valve means and deformable wings near the distal end. The end-hole valve means functions to curtail undesirable jet effects and to decrease the amount of contrast material and radiation required for optimal angiographic results. The deformable wings adjacent the distal end function to facilitate low-pressure entry of contrast material at a high rate of flow to optimize chamber opacification and increase the patient""s safety and comfort.
Thus, one object of the present invention is to provide a catheter in the form of a hollow, thin-walled tube having a plurality of circumferentially-spaced longitudinally extending slits through the thin wall adjacent the distal end. These slits form a plurality of circumferentially-spaced longitudinally extending flexible intermediate portions of the thin wall adjacent the slits. The flexible intermediate portions are capable of forming a plurality of wings extending from the tube to provide for the discharge of fluid from the passageway out through the open slits of the tube near the distal end.
A further object of the present invention is to provide a flexible intermediate portion, shaped during fabrication to retain a winged shape at the distal end. An external, removable cannula dimensioned to sealingly fit over and collapse the tube to its maximum length and minimum width and to compress the wings until they return to a position flush with the wall of the tube can be incorporated.
Still another object of the present invention is to provide a catheter including and insertable over a guidewire or other device to facilitate entry of the catheter""s distal end into a blood vessel. The catheter may also include a valve sealingly fit into the distal end of the main passageway, wherein the valve opens during the passage of the guidewire through the tube and valve. The catheter may otherwise include a valve for at least partially closing the main passageway at the distal end of the tube, wherein the valve comprises a plurality of resilient flaps which flex when exposed to the force of fluid pressure originating within the passageway.
The apparatus of the present invention, including an end-hole valve means as well as a plurality of circumferentially-spaced intermediate portions capable of forming wings, increases the likelihood of satisfactory vessel or chamber opacification, decreases the number of cardiac arrhythmias and endocardial damage resulting from pressure jet effects, and decreases the amount of contrast material and radiation required for optimal chamber or vessel opacification when used in cardiac angiography, without significantly reducing the catheter""s resistance to buckling when used in highly tortuous endocardial procedures.
Still other objects and advantages of the present invention will become apparent to those skilled in the art as the disclosure is made in the following description of the best mode contemplated by me of carrying out my invention. As will be realized, the invention is capable of other embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.